Display screen or portion thereof with an icon



FIG. 1 is a front view of a display screen or portion thereof with an icon, showing our new design; and,

FIG. 2 is another front view thereof, as shown in a display screen environment.

The dash-dot broken lines in the drawings illustrate portions of the display screen and forms no part of the claimed design. The even broken lines showing the electronic device is provided for the purposes of illustrating environmental structure and also forms no part of the claimed design. 

CLAIM We claim, the ornamental design for a display screen or portion thereof with an icon, as shown and described. 